Re: org-src--contents-for-write-back : preserve original major-mode, and avoid mixing tabs and spaces in org-mode buffers

[Nicolas Goaziou <mail@nicolasgoaziou.fr>]

Hello,

Brent Goodrick <bgoodr@gmail.com> writes:

> I found a bug in org-mode where emacs-lisp code that is in a
> already-indented source block in an org-mode buffer is improperly
> indented when editing it via C-c '. Take the following contrived
> example emacs-lisp source code:
>
>  1. Here is a list item with a emacs-lisp source block:
>
>     #+BEGIN_SRC emacs-lisp :results value
>       (let ((uuid "c2327c73-6da3-4421-8bda-194783a00e8f"))
>         (progn
>           (let ((xxx 'yyy))
>             (let ((xxx 'yyy))
>               (while t
>                 (message "infinite loop"))))))
>     #+END_SRC
>
>
> After C-c ', indenting it, and C-c ' again, it renders as
> follows (tabs converted to spaces for this email, since I have
> `indent-tabs-mode' set to t in my emacs-lisp mode, which
> is the Emacs default):
>
>  1. Here is a list item with a emacs-lisp source block:
>
>     #+BEGIN_SRC emacs-lisp :results value
>       (let ((uuid "c2327c73-6da3-4421-8bda-194783a00e8f"))
>         (progn
>           (let ((xxx 'yyy))
>         (let ((xxx 'yyy))
>           (while t
>             (message "infinite loop"))))))
>     #+END_SRC
>
> Notice how the indentation looks bad due to the mixture of tabs
> and spaces.

Indeed. Thank you.

> The bug is in the `org-src--contents-for-write-back' function. It
> uses a temp buffer. The temp buffer's major-mode is left to be
> the default, which is fundamental-mode, which knows nothing about
> how to indent lisp code properly.

And it doesn't need to. This function doesn't care about the code, but
indents it rigidly according to original source block.  IOW, I don't
think changing the major mode is required.

> So in the fix below, I run the major-mode function from the original
> buffer. But even with that fix, the indentation must also use spaces
> in order to avoid mixing tabs and spaces in the resulting Org buffer.

Why do you think it is a good thing that tabs and spaces shouldn't be
mixed. For example, imagine that the source code requires
`indent-tabs-mode' being non-nil, but Org source buffer indentation is
space only, i.e., with `indent-tabs-mode' being nil.

Shouldn't the resulting block be indented with spaces from column 0 to
block boundaries' indentation, and then follow with space indentation?

WDYT?

Regards,

-- 
Nicolas Goaziou